The present invention relates to a multiple type, heat pump type air conditioner in which a plurality of interior units are operated simultaneously or individually by utilizing a vapor compression refrigerating cycle. More particularly, it is suitable for a heat pump type air conditioner used in a cold district where the exterior air temperature decreases, for example, below xe2x88x9215xc2x0 C. in winter.
A technique in which a high-pressure liquid refrigerant is injected into a compression mechanism of a compressor (liquid injection) and the flow rate thereof is controlled to deliver a high heating capability even in a cold district has been known, and is described in JP-A-8-210709 specification, for example.
Also, a technique in which when a plurality of compressors are provided in parallel, liquid injections with flow rate control are respectively provided in order not to stop all compressors at the time of maintenance is described in JP-A-7-151396 specification.
Further, a technique in which a supercooler is integrally provided with an exterior heat exchanger at a lower part thereof to prevent the lower part of the exterior heat exchanger from being frosted and to further increase the heating capability and the coefficient of performance is described in JP-A-9-229496 specification, for example.
In the technique described in JP-A-8-210709 specification, which is a prior art, since only one capacity control type compressor is used, the size of the compressor must be made larger to increase the capacity, so that this technique is unfavorable in view of standardization of production facility or the like. Also, in order to decrease a minimum capability for energy saving, that is, to increase a difference between the maximum and minimum capabilities, it is necessary to further decrease the minimum rotational speed of the compressor. If the minimum rotational speed is decreased, it becomes difficult to form oil film on bearings, so that improvement in the bearings and an oil feeding mechanism is further required.
An object of the present invention is to solve the problems with the prior art, and to provide a highly reliable heat pump type air conditioner in which a difference between the maximum and minimum capabilities is increased without increasing the size of a compressor.
Also, another object of the present invention is to enable the standardization of compressor and facilitate the expansion of product range regardless of the capability required for an air conditioner.
Further, still another object of the present invention is to enable substantial heating operation even if the exterior air temperature is below xe2x88x9215xc2x0 C. by obtaining a high heating capability.
Further, still another object of the present invention is to prevent frosting and icing at the lower part of an exterior heat exchanger even if the heat exchange amount in the exterior heat exchanger increases at the time of heating operation, and to thereby increase the heating capability.
The present invention solves at least one of the above-described problems and achieves at least one of the above-described objects.
To attain the above objects, the present invention provides a heat pump type air conditioner comprising: an exterior unit including an exterior heat exchanger, a plurality of compressors, a four-way valve, an exterior expansion device, and an injection circuit for injecting the liquid refrigerant into each of said plurality of compressors; and a plurality of interior units, each of which includes an interior heat exchanger, connected to said exterior unit, wherein said exterior unit further comprises means for controlling flow rate of the liquid refrigerant to be injected in accordance with number of said plurality of interior units.
With this structure, amounts of liquid injection into the compressors are respectively controlled in accordance with the number of interior units. Therefore, even if the necessary capacity increases and the compressors are operated at a high compression ratio, the compressors are cooled accordingly. As a result, the temperature in the compressors does not increase abnormally, thereby achieving a high efficiency. Further, the minimum rotational speed need not be decreased for one compressor even if a difference between the maximum and minimum capabilities is increased. Therefore, the size of compressor need not be increased, and the formation of oil film on bearings can be made easy, so that the reliability can be enhanced.
Also, the present invention provides a heat pump type air conditioner comprising: an exterior unit including an exterior heat exchanger, a plurality of compressors including a capacity variable type compressor of which rotational speed is controlled, a four-way valve, an exterior expansion valve, and an injection circuit for injecting the liquid refrigerant into each of said plurality of compressors; and a plurality of interior units, each of which includes an interior heat exchanger, connected to said exterior unit, wherein said air conditioner further comprises: a liquid injection expansion valve provided in said injection circuit; and a flow rate controlling means for controlling degree of opening of said liquid injection expansion valve.
In this air conditioner, a plurality of compressors are provided, the liquid refrigerant is injected into each of the compressors, and at least one compressor comprises a capacity variable type compressor of which rotational speed is controlled. Therefore, even if high pressure ratio operation is performed at the maximum capacity, the compressor is cooled accordingly. At the minimum capacity, the capacity can be controlled so as to be the minimum. Therefore, the difference between the maximum and minimum capabilities can be increased further.
Further, in the above-described heat pump type air conditioner, it is preferable that the capacity variable type compressor comprises a scroll compressor in which liquid injection is effected at an intermediate portion between a suction portion and a discharge portion of said compressor.
Further, it is preferable that the injection circuit comprises circuit portions respectively provided for said plurality of compressors, and said flow rate controlling means comprises devices respectively provided in said injection circuit portions.
Further, preferably, a supercool heat exchanger is provided at the lower part of the exterior heat exchanger.
Further, preferably, the plurality of compressors include a scroll type compressor, and the air conditioner further comprises: a liquid injection expansion valve provided in the injection circuit; a flow rate controller for controlling degree of opening of the liquid injection expansion valve; and a controller which, when an exterior air temperature is low, causes the interior heat exchanger to be operated as a condenser and controls said four-way valve so that an interior of a room is heated.
With this, since at least one of the compressors is made of a scroll type, which is suitable for low-speed rotation to high-speed rotation, and the interior of a room is heated even if the exterior air temperature is xe2x88x9215xc2x0 C. or lower, a clean electric air conditioner which is easy to handle can be provided even in a district where the lowest exterior air temperature ranges from xe2x88x9215xc2x0 C. to xe2x88x9220xc2x0 C., for example, in Asahikawa in Hokkaido without the use of an energy source other than electricity such as kerosene and gas.
Further, the present invention provides an exterior unit comprising: an exterior heat exchanger; a plurality of compressors including a capacity variable type scroll compressor; a four-way valve; an exterior expansion valve; an injection circuit for injecting the liquid refrigerant into each of said plurality of compressors; a liquid injection expansion valve provided in said injection circuit; and a flow rate control means for controlling opening degree of said liquid injection expansion valve. The exterior unit is operated so that the capability from the minimum to the maximum is variable in a range of 10% to 130% of a rated capability.
At least one of the compressors is made of a scroll type, which is suitable for low-speed rotation to high-speed rotation, the liquid refrigerant is injected into each of the compressors, and the operation is performed by varying the capability in the range of 10% to 130% of a rated capability. Therefore, the compressor can be standardized without increasing the size of the compressor regardless of the necessary capability.
Further, the above-described exterior unit preferably comprises an injection circuit for injecting the liquid refrigerant into each of the compressors; a liquid injection expansion valve provided in the injection circuit; and a flow rate controller for controlling the degree of opening of the liquid injection expansion valve.
Further, in the above-described heat pump type air conditioner, it is preferable that the plurality of compressors include a capacity variable type compressor of which rotational speed is controlled, and that the air conditioner further comprises, a liquid injection expansion valve provided in an injection circuit portion of the injection circuit for the capacity variable compressor, liquid injection electromagnetic valves respectively provided in injection circuit portions of the injection circuit for compressors other than the capacity variable compressor, and a flow rate controller for controlling degree of opening of the liquid injection expansion valve and opening/closing of the electromagnetic valves.